1. Field of the Invention
The present invention relates to resin compositions and particularly to resin compositions used for semiconductor devices, which must have excellent electrical and mechanical characteristics. Specifically, the present invention relates to an adhesive used for semiconductor devices. More specifically, the present invention relates to an adhesive film used in tape automated bonding (TAB), which is a method for packaging semiconductor devices, to an adhesive sheet used for bonding semiconductor integrated circuits to an interposer, which is a substrate for connecting semiconductor integrated circuits, in order to package the circuits by wire bonding, and to a semiconductor device using the adhesive film and sheet.
2. Description of the Related Art
In general, as ambient temperature increases, resin molecules become active, so that the length and the volume of the resin increase and the elastic modulus deteriorates. Resin compositions whose size and elastic modulus easily change, traditionally, cannot be used in high-precision processing. Also, when a resin composition laminated with a different material, such as, metals or ceramics, is subjected to, for example, a heat cycle test in which heating and cooling are repeated, the difference between the thermal expansion coefficients of the resin composition and the different materials causes an internal stress and degrades elasticity. As a result, the adhesion between the laminated layers is degraded and, in some cases, delamination occurs. In addition, resin compositions used as adhesives for semiconductor devices are required to have sufficient adhesion even under conditions during the heat cycle test and reflow soldering.
It is known that degrading the elastic modulus of the resin compositions increases the adhesion of the resin compositions. However, this leads to an increased thermal expansion coefficient and the elastic modulus is significantly reduced at high temperature. As a result, the adhesion is degraded and the solder reflow resistance is poor.
On the other hand, in order to reduce the thermal expansion coefficient and to increase the elastic modulus of the resin compositions, the cross-linking density of the resin compositions is increased or a hard structure, such as benzene ring, is introduced. These methods are effective to increase the elastic modulus but do not sufficiently reduce the thermal expansion coefficient. As a result, shrinkage on curing of the resin compositions increase internal stress and the increased elastic modulus easily causes brittle fracture to occur in the adhesive resin composition. Thus, the adhesion of the resin compositions is degraded. Also, in another method, glass fiber, inorganic particles of silicon oxide, or the like are added to a resin material whose elastic modulus is low at room temperature to reduce the thermal expansion coefficient and to increase the elastic modulus at high temperature of the resin composition. However, in this instance, a large amount of inorganic component have to be added, and consequently the proportion of organic components is relatively reduced, so that the resulting resin composition becomes brittle and the adhesion of the resin composition is significantly degraded.
FIGS. 1-6 are TEM pictures of resin composition showing a matrix phase and a disperse phase. The TEM pictures include the magnification scale.
Accordingly, an object of the present invention is to provide a highly adhesive resin composition having a high solder-reflow resistance, a low thermal expansion coefficient, and a high elastic modulus.
The present invention is directed to a resin composition comprising: a phase separation structure having at least two phases; and inorganic particles having a mean primary particle size of 0.1 xcexcm or less.
The content of the inorganic particles may be in the range of 5 to 50 weight percent.
Preferably, the phase separation structure comprises a matrix phase and a disperse phase.
Preferably, the inorganic particles are mainly present in either the matrix phase or the disperse phase.
Alternatively, the inorganic particles may be mainly present in the interface between the matrix phase and the disperse phase.
Preferably, at least one of the matrix phase and the disperse phase forms a chain structure.
Preferably, the area ratio of the matrix phase is in the range of 50 to 95 and the area ratio of the disperse phase is in the range of 5 to 50.
Preferably, the elastic modulus of the resin composition after being cured is 25 MPa or more at a temperature of 150xc2x0 C.
Preferably, the ratio of the elastic modulus of the resin composition at 30xc2x0 C. to the elastic modulus at 150xc2x0 C. is 30 or less.
The present invention is also directed to an adhesive film for semiconductor devices. The adhesive film comprises an organic insulating layer and an adhesive layer formed on a surface of the organic insulating layer. The adhesive layer comprises the resin composition described above.
The adhesive film may further comprise a protective layer capable of being peeled.
The present invention is also directed to a metallic foil-laminated film comprising the above-described adhesive film and a metallic foil laminated on the adhesive layer of the adhesive film.
The present invention is also directed to a semiconductor device comprising the metallic foil-laminated film.
By using the resin composition of the present invention, which has a low thermal expansion coefficient and a high elastic modulus, as an adhesive for semiconductor devices, a semiconductor device including an adhesive layer having excellent reflow soldering resistance and adhesion can be achieved.
A resin composition of the present invention has a phase separation structure between at least two phases and contains inorganic particles having a mean primary particle size of 0.1 xcexcm or less.
The inorganic particles are not limited to being spherical but may be elliptical, flake, rod-like, or fibrous. The mean primary particle size of the inorganic particles is 0.1 xcexcm or less and preferably in the range of 1 nm to 0.08 xcexcm. A mean primary particle size larger than 0.1 xcexcm makes it difficult to reduce the thermal expansion coefficient of the resin composition and to increase the elastic modulus. The mean primary particle size here means the highest frequency in the particle size distribution of the inorganic particles when they exist independently. The mean primary particle size also represents the diameter of the particles when they are spherical and the maximum length when they are elliptical or flat. When the particles are rod-like or fibrous, the mean primary particle size represents the maximum length in the longitudinal direction of the particles. The mean primary particle size of inorganic particle powder can be measured by a laser diffraction/scattering method or a dynamic light scattering method. However, the measuring method needs to be appropriately selected depending on the particle shape, the method for preparing the particles, the medium for dispersing the particles, and the method for dispersing the inorganic particles.
The content of the inorganic particles is in the range of 5 to 50 weight percent relative to the solid contents in the resin composition and preferably in the range of 7 to 30 weight percent. A content of the inorganic particles smaller than 5 weight percent makes it difficult to reduce the thermal expansion coefficient of resin composition and to increase the elastic modulus. A content of the inorganic particles more than 50 weight percent gradually degrades the adhesion of the resin composition.
Any inorganic particles including ceramics may be used in the present invention. Exemplary ceramic particles include simple ceramic powder, powder mixture of glass and ceramics, and crystallized glass.
Simple ceramic powder includes alumina (Al2O3), zirconia (ZrO2), magnesia (MgO), beryllia (BeO), mullite (3Al2O3.2SiO2), cordierite (5SiO2.2Al2O3.2MgO), spinel (MgO.Al2O3), forsterite (2MgO.SiO2), anorthite (CaO.Al2O3.2SiO2), celsian (BaO.Al2O3.2SiO2), silica (SiO2), enstatite (MgO.SiO2), and aluminium nitride (AlN). Preferably, the purity of these ceramic powders is 90 weight percent or more. When aluminium nitride powder is used, 0.5 to 20 weight percent of calcium additives, such as CaC2, CaVO3, CaCN2, CaF2, and CaO, or of yttrium additives, such as Y2O3, may be added to the powder. Powder mixtures may be added which contain: 0.01 to 15 weight percent, on a metal element basis, of additives including yttrium, rare-earth metals, alkaline-earth metals, and carbon; 1 to 5 weight percent of carbides, such as MgC2, ZrC, VC, and NbC; or oxides, such as BeO. A preferred content of additives is 1 to 10 weight percent of Y2O3 and BeO, 1 to 5 weight percent of calcium oxide, or 1 weight percent or less of carbon. A single additive or a mixture of two or more additives may be used.
The powder mixture of glass and ceramics is, for example, a glass composition powder containing SiO2, Al2O3, CaO, or B2O3, and if necessary, MgO, TiO2, or the like. Specifically, the powder mixture of glass and ceramics contains SiO2xe2x80x94B2O3 glass, PbOxe2x80x94SiO2xe2x80x94Al2O3xe2x80x94B2O3 glass, CaOxe2x80x94SiO2xe2x80x94Al2O3xe2x80x94B2O3 glass, or the like and at least one ceramic component selected from the group consisting of alumina, zirconia, magnesia, beryllia, mullite, cordierite, spinel, forsterite, anorthite, celsian, silica, and aluminium nitride.
The crystallized glass is, for example, MgOxe2x80x94Al2O3xe2x80x94SiO2 and Li2Oxe2x80x94Al2O3xe2x80x94SiO2 crystallized glass. The crystallized glass is prepared such that, for example, B2O3 and a nucleating material are added to MgOxe2x80x94Al2O3xe2x80x94SiO2 glass, followed by being calcined at a temperature of 900 to 1000xc2x0 C. to separate out cordierite crystals to increase the strength thereof, or such that a nucleating material is added to LiO2xe2x80x94Al2O3xe2x80x94SiO2 glass, followed by separating out spodumene to increase the strength thereof.
Diatomite, zinc oxide, calcium carbonate, mica, fluorocarbon resin powder, diamond powder, and the like may be used as the inorganic particles.
The inorganic particles may be subjected to surface treatment, if necessary. Exemplary surface treatments include water-repellent treatment using silicone oil or the like, hydrophobic treatment or hydrophilic treatment using silane coupling agent or the like, and introduction of or an organic functional group, such as a hydroxyl group, an amino group, a carboxyl group, an epoxy group, an acrylic group, a vinyl group, an alkyl group, or an aryl group. The surface treatment is appropriately selected to improve affinity with the resin composition, cohesion in the interface between the inorganic particles and resin composition, dispersion or the like.
The phase separation structure in the present invention means that a plurality of phases is present in organic components of the resin composition and the conformation of phases may have disperse/matrix phases, a lattice laminate structure (lamella-like structure), or others. Preferably, the phase separation structure has a matrix phase and a disperse phase. The matrix phase refers to the main phase in the phase separation structure of a cured resin composition. The disperse phase refers to a phase in the matrix phase, and may have any shape including a sphere, cylinder-like shape, and indefinite shape. Preferably, a plurality of disperse phases forms a chain structure. In the chain structure of the disperse phase, two or more independent disperse phases are linked and form any one of a linear, a comb, an dendritic, and an asteriated structure to form a higher order network structure.
Preferably, the area proportions of the matrix phase and the disperse phases are in the range of 50 to 95% and in the range of 5 to 50%, respectively.
Preferably, the content of the inorganic particles in the resin composition is in the range of 5 to 50 weight percent. Preferably, the inorganic particles are mainly present in either the matrix phase or the disperse phases, but not present in both phases uniformly. The inorganic particles may be mainly present in the interfaces between the matrix phase and the disperse phases, and preferably they are mainly present in the vicinity of the interfaces in the matrix phase. Still more preferably, the disperse phases form a chain structure in which at least two disperse phases are linked and the inorganic particles are mainly present in the vicinity of the interfaces between the matrix phase and the disperse phases in the matrix phases, or the disperse phases form the chain structure in which at least two disperse phases are linked and the inorganic particles are mainly present in the disperse phases.
The area ratio of the matrix phase to the disperse phases, the formation of a higher order chain structure, and the state of the inorganic particles in the phase separation structure may be determined according to the components in the resin composition and the method for dispersing the inorganic particles.
The matrix/disperse phase separation structure, the dispersion of the inorganic particles, the state and higher order chain structure of the disperse phases are observed by transmission electron microscopy (TEM) in which the resin composition is stained with osmic acid, ruthenium oxide, phosphotungstic acid, or the like, if necessary. The area ratio of the matrix phase to the disperse phases is observed by, for example, image analysis of a TEM photograph. In order to measure the area ratio of the matrix phase and the disperse phases, a transparent film having a uniform thickness and specific gravity may be superposed on the TEM photograph and the areas of the disperse phases are copied on the film, followed by being cut out and being weighed.
Preferably, the elastic modulus of the resin composition after being cured is 25 MPa or more at 150xc2x0 C. Preferably, the elastic modulus ratio at 30xc2x0 C. to 150xc2x0 C. ((elastic modulus at 30xc2x0 C.)/(elastic modulus at 150xc2x0 C.)) is 30 or less. In the best state of the resin composition, the elastic modulus is 25 MPa or more and the elastic modulus ratio at 30xc2x0 C. to 150xc2x0 C. is 30 or less. If the elastic modulus is less than 25 MPa at 150xc2x0 C., heat generated by a bonding device softens the adhesive layer of the adhesive film formed of the resin composition, consequently creating a hollow in a wiring pattern or causing an adhesion failure between a wire or chip and the wiring pattern. If the elastic modulus ratio at 30xc2x0 C. to 150xc2x0 C. is more than 30, a warp is liable to occur in the adhesive film.
More preferably, the elastic modulus is 50 MPa or more and still more preferably 80 MPa or more. Also, more preferably, the elastic modulus ratio at 30xc2x0 C. to 150xc2x0 C. is 20 or less and still more preferably 10 or less.
The resin composition having the above-described characteristics has not been known yet. By adding a small amount of inorganic particles to the resin composition, a reduced thermal expansion coefficient and an increased elastic modulus can be achieved, and the resulting resin composition can be highly adhesive. It is considered that the inorganic particles concentrated in the interfaces between the matrix phase and the disperse phases and existing in the disperse phases allow the disperse phases to form a higher order chain structure so that the longitudinal expansion and the volumetric expansion of the resin composition at heating and cooling are reduced and thus the thermal expansion coefficient is reduced. Also, it is considered that the higher order chain structure inhibits the fluidization of the resin composition and thus the elastic modulus is increased at high temperature.
The resin composition of the present invention having the phase separation structure contains a plurality of resin components including thermoplastic resin or thermosetting resin.
The thermoplastic resin used in the present invention includes polyolefin such as polyethylene, polypropylene, and ethylene copolymers, styrene resins such as polystyrene and ABS resin, polyvinyl chloride, vinylidene chloride, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyacrylate resin, polyoxybenzoyl, polycarbonate, polyacetal, polyphenylene ether, and polyimide, and it is not limited to those as long as it has plasticity at temperatures in the range of 80 to 200xc2x0 C. Preferably, polyamide resins are used in view of stability at high temperature and electrical characteristics. More preferably, a flexible, less water-absorptive polyamide containing dicarboxylic acid having a carbon number of 36 (so-called dimer acid) is used. In general, polyamide resins containing dimmer acid are prepared in the usual process by polycondensation of dimer acid and diamine. At the same time, a dicarboxylic acid, such as adipic acid, azelaic acid, or sebacic acid, may be added as a copolymerization component. The diamine includes ethylenediamine, hexamethylenediamine, and piperazine. From the viewpoint of hygroscopicity and solubility, two or more diamines may be mixed.
Preferably, the content of the thermoplastic resin in the resin composition is in the range of 1 to 90 weight percent. If the content of the thermoplastic resin is less than 1 weight percent, the resulting resin composition does not become flexible, and when it is used as the adhesive layer of an adhesive film for semiconductor devices, a fracture can occur in the adhesive layer. If the content is more than 90 weight percent, the resulting resin composition becomes too flexible to bear a load when semiconductor chips are mounted. Consequently, a large hollow is created in the adhesive layer and thus adhesion failure occurs. Preferably, the content of the thermoplastic resin is in the range of 20 to 70 weight percent.
The thermosetting resin used in the present invention includes phenol novolac epoxy compounds; cresol novolac epoxy compounds; bisphenol A epoxy compounds; bisphenol F epoxy compounds; bisphenol S epoxy compounds; epoxy compounds derived from a thiodiphenol, phenol, or naphthol aralkyl resin having a xylylene bridge; epoxy compounds derived from a phenol-dicyclopentadiene resin; alicyclic epoxy compounds; heterocyclic epoxy compounds; glycidyl ester epoxy compounds produced by reaction of a polybasic acid, such as phthalic acid or dimmer acid, with epichlorohydrin; glycidilamine epoxy compounds produced by reaction of a polyamine, such as diaminodiphenylmethane, diaminodiphenylsulfone, or isocyanuric acid, with epichlorohydrin; brominated epoxy compounds; and epoxy compounds having a cyclohexene oxide structure, such as xcex5-caprolactone denaturated 3,4-epoxycyclohexylmethyl-3xe2x80x2,4xe2x80x2-epoxycyclohexane carboxylate, trimethylcaprolactone denaturated 3,4-epoxycyclohexylmethyl-3xe2x80x2,4xe2x80x2-epoxycyclohexane carboxylate, or xcex2-methyl-xcex4-valerolactone denaturated 3,4-epoxycyclohexylmethyl-3xe2x80x2,4xe2x80x2-epoxycyclohexane carboxylate. In addition, organopolysiloxane having a glycidyl group and silicone-denaturated epoxy compounds produced by reaction of the above-described epoxy compounds with organosiloxane having a carboxyl group may be sued. At least two compounds of the epoxy compounds and the silicone-denaturated epoxy compounds may be combined.
Preferably, in addition to the epoxy resin, the thermosetting resin contains a curing agent capable of reacting with epoxy resin. Exemplary curing agents include polyamines, such as diethylenetriamine, triethylenetetramine, m-xylenediamine, and diaminodiphenylmethane; polyamides, such as polyamide dimmer; anhydrides, such as phthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, and methyl nadic anhydride; 3-aminophenol; resorcinol; catechol; hydroquinone; pyrogallol; 3-hydroxybenzoic acid; 3-cyanophenol; 2,3-diaminophenol; 2-amino-3-hydroxybenzoic acid; 3-hydroxyphenylacetamide; 3-hydroxyisophthalic acid; 3-hydroxyphenylacetic acid; 3-phenolsulfonic acid; phenolic resins, such as phenol novolac, phenol aralkyl, bisphenol A, and bisphenol F; resol-type phenol resin; tertiary amines, such as polymercaptan, 2-ethyl-4-methylimidazole, and tris(dimethylaminomethyl)phenol; and Lewis acid complexes, such as boron trifluoride ethylamine complex, but the curing agents are not limited to these.
Preferably, phenol resins are used as a curing agent for the thermosetting resins and the epoxy resins. Phenol resins are compatible with polyamides, and serve as a suitable blending material to give the polyamides adequate thermal resistance and disruptive strength when the polyamides are set. The thermal resistance and the disruptive strength are important to the balance between the insulation resistance and the adhesion of the resin composition.
The content of the thermosetting resin in the resin composition which results in the adhesive layer of the adhesive film is in the range of 0.1 to 80 weight percent and preferably in the range of 20 to 70 weight percent. A thermosetting resin content less than 0.1 weight percent reduces the thermal resistance of the adhesive layer and a thermosetting resin content more than 80 weight percent degrades the flexibility of the adhesive layer, and consequently, a fracture occurs in the adhesive layer. Also, a curing accelerator may be added. For example, known accelerators including aromatic polyamine, boron trifluoride amine complexes, such as boron trifluoride triethylamine complex, imidazole derivatives, such as 2-alkyl-4-methylimidazole and 2-phenyl-4-alkylimidazole, organic acid, such as phthalic anhydride and trimellitic anhydride, dicyandiamide, and triphenylphosphine may be used. Preferably, the content of the curing accelerator is 10 weight percent or less in the adhesive layer.
In addition, an organic or inorganic substance, such as an antioxidant or an ion scavenger, may be added unless it degrades the adhesion of the adhesive layer.
The resin composition of the present invention may be used for resin substrates, fibers, undrawn films, drawn films, hot pressing materials, multi layer substrate, metallic foil-laminated substrates, paints, adhesives, and the like. In particular, the resin composition is advantageously used as an adhesive for semiconductor devices because it is highly insulative. Specifically, the resin composition is used for multi layer substrate, adhesive films, adhesive sheets for bonding semiconductors and wiring boards, and metallic foil-laminated substrates.
A protective layer may be formed on an adhesive layer of the adhesive film of the present invention to prevent the adhesive layer from being contaminated by dust, oil, water, and the like. The protective layer also improves the workability when the resin composition is formed into a very thin film. The protective layer may be a polyester or polyolefin film coated with silicone or a fluorine compound or a paper laminated with this polyester or polyolefin, and the protective layer is not limited to these as long as it is capable of being peeled without damaging the resin composition. When protective layers are provided on both surfaces of the resin composition, preferably, the peeling resistance of one protective layer is different from that of the other protective layer. The thickness of the protective layer may arbitrarily be selected, and preferably it is in the range of 10 to 125 xcexcm.
The manufacturing process of the adhesive film and the metallic foil-laminated film for semiconductor devices will now be described. The shape of the adhesive film and the laminate film are not limited and may be tape-like or sheet-like. The adhesive film and the metal-laminated film have a substrate with a thickness of 20 to 125 xcexcm formed of a plastic, such as polyimide, polyester, poly(phenylene sulfide), polyether sulfone, poly(ether-ether-ketone), aramid, polycarbonate, or polyacrylate, or of a composite material, such as glass cloth impregnated with an epoxy resin. The substrate may be formed by laminating a plurality of films selected from these. The substrate may be subjected to surface treatment, such as hydrolysis, corona discharge, cold plasma, physical roughening, and easy-adhesive coating, if necessary. Also, when the stiffness of the substrate is too low to be treated, a stiff film or the like capable of being peeled in a later process may be laminated on the rear surface of the substrate.
The inorganic particles may be mixed into the resin composition using a kneader or the like. Alternatively, an inorganic particle paste or slurry composed of the inorganic particles and a solvent or of the inorganic particles, a solvent, and a resin component may be prepared with a roll mill, a ball mill, or the like and be subsequently mixed with a necessary resin component.
In a mixing process, for example, the inorganic particles, a resin component, and a solvent are mixed. The solvent is capable of dissolving the resins used, and is, for example, methyl cellosolve, butyl cellosolve, methyl ethyl ketone, dioxane, acetone, cyclohexane, cyclopentanone, isobutyl alcohol, isopropyl alcohol, tetrahydrofuran, dimethylsulfoxide, xcex3-butyrolactone, toluene, xylene, chlorobenzene, benzyl alcohol, isophorone, methoxymethylbutanol, ethyl lactate, propylene glycol monomethyl ether and acetate derived from propylene glycol monomethyl ether, N-methylpyrrolidone, water, or other solvents containing at least one of these solvents. A stabilizer, a dispersant, a precipitation inhibitor, a plasticizer, an antioxidant, or the like may be added to the mixture. These materials are mixed with a ball mill, an attritor, a roll mill, a kneader, a sand mill, or the like. Undispersed matter and gelled matter are removed from the resulting resin composition with a filter having a mesh which is coarser than the size of the inorganic particles, if necessary.
The resin composition is dissolved in a solvent and is then applied on a flexible insulating film or a conductive film, followed by being dried to form an adhesive layer. Preferably, the thickness of the adhesive layer is in the range of 0.5 to 100 xcexcm. More preferably, the thickness is in the range of 2 to 25 xcexcm. The applied resin composition is dried at 100 to 200xc2x0 C. for 1 to 5 minutes, and thus an adhesive film is formed. This adhesive film is laminated with the protective film and is slit into strips with a width in the range of 35 to 158 mm. Thus, an adhesive tape used for semiconductor devices is completed. On the other hand, in order to form a metal-laminated film, the adhesive film is laminated with a metallic foil, and, if necessary, it is cured.
The resulting adhesive tape for semiconductor devices and metallic foil-laminated film are used for a semiconductor-connecting substrate, and the semiconductor-connecting substrate is used for a semiconductor device.
Methods for manufacturing an adhesive sheet for semiconductor devices, using the resin composition of the present invention and for manufacturing a semiconductor device using the adhesive sheet will now be described. The resin composition is dissolved in a solvent and is then applied on a polyester film having low peeling resistance, followed by being dried. The surface of the resin composition applied on the polyester film is laminated with a polyester or polyolefin protective film having much lower peeling resistance, thus resulting in an adhesive sheet. The resulting adhesive sheet is subjected to thermocompression to be bonded to a copper-laminated TAB tape with wiring. The other surface of the adhesive sheet is also subjected to thermocompression to be bonded to an IC and is then cured at 120 to 180xc2x0 C. The IC and a wiring board are joined with each other by wire bonding and are then sealed with a resin. Finally, solder balls are formed by solder reflow, and thus a semiconductor device is completed.
According to the above, the adhesive film for semiconductor devices, the metallic foil-laminated film, the semiconductor-connecting substrate, the adhesive sheet for semiconductor devices, and the semiconductor device can be formed.